Tree shaking machines are hydro-mechanical systems generally used for nut and fruit harvesting (e.g., almonds, walnuts, pecans, pistachios, cherries, etc.). Tree shaking technologies were developed as early as the 1960s, and were initially developed for harvesting fruit from nut and olive trees. Many inertial shakers that are used today were developed in the early 1970s. Generally, conventional tree shakers are of two types: (1) a slider crank mechanism, which may or may not be an inertia type shaker, and which provides a linear shaking motion, and (2) a mechanism that uses rotating eccentric masses which normally do not provide linear motion.
Linear inertial shakers may utilize the traction of a cable connected to a piston rod-handle system or just by the vibration produced by an eccentric mass in rotation to generate a linear motion. However, the more common shakers utilize rotation of eccentric weight wheels to shake a tree to which the tree shaking machine is attached to thereby create vibrations in the tree to dislodge a crop (e.g., fruit or nut) form the tree. This type of vibration is carried out by the superposition of the frequencies produced by 2 or 3 wheels, with eccentric masses that rotate typically with a frequency between 18 and 40 Hz, accelerating the fruits to separate them from the trees.
Existing tree shakers that utilize eccentric weights have unpredictable moments of force. The moment of force of such machines is typically only rudimentarily characterized by a general shake pattern. These basic patterns are always circular, but they are random and unpredictable because the rotation of the eccentric weights are not closely controlled or coordinated in conventional shakers. Thus, the impact points of the shaker on the tree are also randomized and essentially out of control.
Conventional shakers may move the tree clamp and the attached tree in a randomly changing manner from side-to-side (which is ideal) to a front-to-back (which is imparts little or no movement to the tree), oblique directions therebetween (which provide inefficient shaking), and rotational motion around the axes of rotation (also inefficient movement and may cause wear on the shaker itself). The front-to-back, obliquely, and rotationally applied forces may cause damage to the tree's trunk and limbs and cause excessive heating and clamp wear. Trunk and limb damage includes primarily “barking” damage that may be characterized as tearing or bruising at the cambium layer of the tree, which damages the trees xylem and phloem cells that are responsible for nutrient transfer. Barking may diminish the tree's ability to transfer nutrients to limbs where fruit is grown and can therefore impact the production of the tree. In some instances, tree shakers can result in catastrophic damage to the trunk that renders the tree non-productive (e.g., significant tissue damage to the tree or a wound that results in a devastating infection of the tree, such as a fungal infection). Thus, tree trunk and limb damage can be both acute and cumulative, and can result in significant production loss from an orchard due to the reduction in the productive life span of trees and/or incremental reduction in the production of a damaged tree.
It is therefore desirable to provide an improved tree shaking device that reduces inefficiencies in the transfer of energy from the shaker head to the structure or object engaged by the shaker head (e.g., a fruit or nut tree), and that reduces the amount of damage to the trunk and limbs of trees engaged by the shaker head. The present invention provides such apparatuses and methods of using the same, while at the same time accomplishing many of the desirable conditions described above.